1. Field of the Invention
This invention relates to an apparatus and method for the fixation of proximal humerus fractures in which one or more bone pieces must be aligned with the major portion of the bone. In proximal humerus fractures, displacing forces such as muscle connections acting on the fragments of the fracture frequently cause bone fragments to separate and pull away from the main part of the humerus. In alternative embodiments, this invention provides an apparatus and methods for internal fixation of fractured humerus bones, nonunions, and primary and metastatic tumors, in each case providing anatomic alignment to reduce impingement and promote healing.
2.Description of the Related Art
The conventional methods and apparatuses for treating proximal humerus fractures have respective shortcomings relating to effective treatment of many of the numerous categories of fractures. These categories correspond to proximal humerus fractures having predictable patterns. Specifically, displaced proximal humerus fractures are classified according to the displacement of humerus segments. Various apparatus and methods appear in the related art for treating proximal fractures of the humerus, including plates, screws, sutures and rods, but none of these solve all of the problems relating to fixation of these fractures.
One major problem in treating humerus fractures is the difficulty of finding adequate bone stock to secure the related art internal fixation means. The related art methods of fixation are therefore frequently difficult and unsuccessful, leading to possible loss of fixation, loss of fracture reduction, nonunion or malunion. Further, in many cases these methods do not allow early motion. Early motion is beneficial for cartilage nutrition and to prevent intraarticular adhesions and shoulder stiffness.
Some related art methods of fixation employ sutures attached to the rotator cuff musculature. Such a means of fixation does not provide the ease, anatomic alignment, and stability of the present invention, thereby also possibly leading to loss of fracture reduction or fixation.
A first conventional device, such as is shown in U.S. Pat. No. 4,919,670 to Dale et al., includes a stem portion for insertion into the intramedullary canal of the humerus and a head portion to replace the head of the humerus. This type of device is ineffective, however; at assisting in the fixation of bone fragments such as the lesser or greater tuberosity, or when the head of the humerus is to be saved. For example, the modular humeral prosthesis is designed to replace the natural humerus head and is not designed for a situation wherein the proximal humerus is fractured but the head is still attached or can be salvaged.
Another related art device is shown in U.S. Pat. No. 5,066,296 to Chapman et al describes an intermedullary rod used in the treatment of bone fractures. The Chapman apparatus utilizes an elongated body member inserted into a bone cavity and a tab member attached to the body member by a separate screw. The tab member has a transverse clearance aperture created prior to the tab member's attachment to the body member. A screw passes through the pre-formed clearance aperture, threads into a bone mass and pulls the bone against the tab member. The screw threads do not engage the tab member. Further, locking tabs on the tab member engage recesses on the body member, thereby eliminating any opportunity to rotate the tab member to selectively position the tab member aperture. This restriction limits the flexibility of this related art because, frequently, the pre-installed aperture cannot be optimally positioned. Further, this Chapman apparatus is applicable to diaphyseal fractures, i.e., fractures of the main bone shaft, and not metaphyseal or epiphyseal fractures such as proximal humerus fractures
Still another related art device is shown by U.S. Pat. No. 5,112,333 to Fixel and relates to fixation of femoral and tibial bone fractures. This type of intramedullary nail provides fixation of fractures of bone shafts, in which the intramedullary nail provides compressive force to the separated shaft portions. The Fixel intramedullary nail, however, is not addressed to, nor effective for, proximal humerus fractures, particularly the segmented proximal humerus fractures. The reason that Fixel, and similar, methods are not effective for such segmented fractures is that the intramedullary nail secures bone fragments using individual screws attached to bone and traversing through the nail to attach to bone as well. With segmented proximal humerus fractures, however, there is frequently little bone stock suitable for the screws to anchor to, and the bone that is available is frequently weak. Further, in one embodiment directed toward the fixation of distal femoral or tibial fractures, the Fixel method requires the individual screws to pass through the slotted tip of the nail, thereby limiting the possible directions of approach. This may serve for femoral and tibial fractures, but is unlikely to work for proximal humerus fractures with its accompanying complex anatomy and fracture patterns. The reason is that, for such complex anatomy and fractures, there is need for significant freedom in the placement of fixation screws to allow the surgeon to capture each of the individual fracture fragments and fixate them. The alternative means employed by the intramedullary nail to secure bone fragments involves a plate, and a plate is not appropriate for use in many proximal humerus fractures wherein the strength of surrounding soft tissue or musculature and not the bone itself is the best means available for stabilizing the fracture. Additionally, a plate is very prominent, and may cause impingement.
Another related art device is described, for example, within U.S. Pat. No. 5,201,733 to Etheredge, III, and relates to the fixation of a bone fracture in which fractured bone pieces are first positioned and held in place with preferably bioabsorble screws and pins. Metal reconstruction plates are then attached to the external surface of the bone with screws, clamps, or pins, without regard to the location of the underlying bioabsorbable screws and pins. This Etheredge and related methods therefore rely on the strength of the bone to hold the plate, and in many patients with proximal humerus fractures the bone quality is not adequate for such fixation, thereby incurring the risk of loss of fixation of the fracture. Further, this method is generally ineffective in a proximal humerus fracture wherein multiple bone fragments are separated from the humerus. This is because a straight plate is not appropriate on a rounded humerus fragment, such as a head. Therefore, this Etheredge and related plate methods are best applicable for diaphyseal fractures only, not the metaphysical and epiphyseal types such as those that occur with proximal humerus fractures.
Another shortcoming of plate methods is that the installation of a plate involves stripping of the soft tissues from the bone. This is necessary for the plate to lie flat on the bone. The stripping, however, inhibits subsequent blood supply to the fragments because the soft tissue attachments provide that blood supply. This blood supply reduction can retard healing of the bone. Therefore, any fixation applied to the superficial surface of the bone risks damage to the blood supply of the bone fragments.